Paramedics are responsible for the care of patients requiring emergency assistance in the out of hospital setting. These health care providers need to make many decisions during the course of an emergency call. This thesis on paramedic clinical decision-making includes two studies, intended to determine which decisions paramedics make that are most important for patient safety and clinical outcome, and what thinking strategies paramedics rely on to make decisions. Forty-two decisions were found to be most important for outcome and safety. The highest decision density of an emergency call is during the on-scene treatment phase. Paramedics use a mix of thinking strategies, including rule out worst scenario, algorithmic, and exhaustive thinking. The results of these studies have implications for future research, paramedic practice and training.